There are numerous electronic lock and key circuits available. U.S. Pat. No. 3,787,714, "Electronic Lock and Key Systems Employing Paired Key and Master Coding Modules", discloses a system for activating an electric latch when a valid key is inserted into a key receiving receptacle. The system is energized by the insertion of the key into the receiving receptacle to energize both the key and the master coding card to cause a correlation sequence to be implemented to determine whether information contained on the key is valid by comparing this information with the predetermined information on the master coding card.
U.S. Pat. No. 4,079,356, "Coded Electronic Lock and Key", discloses an electronic key comprising a first binary counter and a first multiplexer for pulse code modulating a uniform clock pulse train to produce a first coded pulse train modulated within a given code. The key is connected to an electronic lock comprising: (i) a second binary counter and a second multiplexer for pulse code modulating the same clock pulse train to produce a second coded pulse train modulated with the same code; (ii) an exclusive OR gate to which said first and second multiplexers are connected; (iii) a first NAND gate having one input connected to the output of the exclusive-OR gate; (iv) a flip-flop or binary counter having its clock input connected to the output of the NAND gate; (v) an initial logical one output connected to a second input of the NAND gate; (vi) a second NAND gate having one input connected to the output of the flip-flop or counter and another input connected to the output of the second multiplexer; and (vii) a binary counter having its clock input connected to the output of the second NAND gate. The output of the lock is taken from one of the counting outputs of the output counter.
Still further, U.S. Pat. No. 4,723,121, "Electronic Locking Apparatus for Motor Vehicles", discloses an electronic key and an electronic lock with each containing a synchronized, constantly operating, precision oscillator.
There is a need for allowing certain passengers entering car calls or hall calls to be serviced prior to other passengers. This need to "unlock" the elevator system for select persons and further provide them priority service is not met by any of these lock and key schemes.